Stated most simply, permanent wave hair dressing is accomplished by rolling a length of hair onto a roller, applying a first liquid chemical to the hair to induce a permanent wave, allowing a length of time to pass, and then applying a second liquid chemical to the hair to stop the permanent waving action of the first liquid chemical. Normally, a segment of paper is rolled along with at least the end of each length of hair to protect the hair from frizzing and the like during the permanent wave process. Appropriately, this paper is commonly referred to as end paper.
It is important to note that there are variables that affect the condition of permanent waves such as differences in hair properties including hair condition and health, the type of permanent wave liquid chemical used, temperature and time, and hairdresser skill and experience. Unfortunately, these factors are not easily controllable. During permanent waving, the condition of the waves must be ensured by feel and observation and is directly related to the proper and thorough saturation of the end papers with the respective permanent wave liquid chemical during application by the hair dresser. If the end papers are not sufficiently and uniformly saturated, the resulting permanent wave will be incomplete or otherwise unacceptable.
Such imperfections are a common occurrence because with presently available end paper it is difficult to observe and determine when the end papers are fully saturated since there is no clear visual differentiation between wet and dry portions of the end paper. For example, where a prior art strip of end paper is white in color, there is substantially no difference in appearance between a wet and a dry portion of a piece of end paper. This problem is particularly prevalent when multiple liquid chemicals are applied during the hair dressing process such as with the application of a permanent wave lotion followed by a permanent wave neutralizing agent. Hairdressers typically must rely on experience and judgment to determine whether hair has been adequately saturated with the permanent wave lotion and the permanent wave neutralizing agent. This reliance often results in either over or under application of the respective liquid chemical with a multiplicity of consequent disadvantages. For example, there may be a waste of liquid chemical, poor wave quality, an increase in hairdressing time, as well as customer dissatisfaction.
Certainly one knowledgeable in the art will be aware that the prior art has attempted to provide indications of the completion of a permanent wave process. For example, in U.S. Pat. No. 4,398,183 to Ando, a lead acetate paper is located adjacent hair undergoing a permanent wave, and a complex detecting apparatus with a light emitting diode and a light receiving portion triggers a buzzer device when a chemical reaction between the lead acetate paper and a volume of hydrogen sulfide gas emitted by the permanent wave process changes the lead acetate paper from brown to black thereby indicating that the permanent wave is complete. As a result, it becomes clear that the Ando patent presents a complicated, costly, cumbersome and impractical method and device. Furthermore, the Ando apparatus is capable of indicating only whether a permanent wave is complete; there is no indication as to whether a given length of hair has been saturated by a permanent wave liquid chemical. Consequently, the Ando apparatus may provide a positive indication of a complete permanent wave process notwithstanding the fact that one or more permanent wave liquid chemicals have been hopelessly misapplied.
In light of the above, it becomes clear that there is a great need in the art for a permanent wave end paper and method that permit a user to ensure that the permanent wave end paper and thus the length of human hair with which the end paper is rolled have been completely saturated with the permanent wave liquid chemical. Certainly, a permanent wave end paper that is simple in use and economical in manufacture and that would demonstrate a change in color in response to saturation by a permanent wave liquid chemical would be ideal.